Leveraging Dynamic Bonds to Probe Equilibrium Topology in Polymer Networks

Abstract

Formation of chemically cross-linked polymer networks is a kinetically driven process leading to local topological defects such as primary loops, which decrease the elastic effectiveness of the network. Dynamic bonds in a network create possibilities for bond exchange and network rearrangement, potentially altering the topology. This work investigates how network topology changes as a result of incorporating dynamic bond rearrangements into an irreversibly cross-linked network. Kinetic Monte Carlo simulations and experimental validation reveal that incorporating dynamic bond rearrangements leads to a lower primary loop fraction and higher modulus. Such rearrangements lead to the formation of a more strongly percolated structure and a greater number of higher-ordered cyclic structures in comparison to kinetically cross-linked networks. The quantitative change in the topology is dependent on the concentration and equilibrium constant, demonstrating that irreversible cross-linking occurs by an out-of-equilibrium process and that dynamic bonding can tune network topology.